| The Surgical Technologist | APRIL 2022 164 leads to problems with fit, comfort, and the overall design and appearance.24 Three-dimensional printing has simplified the manufacturing process while facilitating a design that integrates the unique biomechanical metrics of each individual. For patients with plantar fasciitis, these 3D-printed AFOs have shown favorable outcomes.25 An example of a 3D-printed AFO is shown in Figure 4. Three-dimensional printing has reached patients’ homes with the introduction of the desktop 3D printer. The straightforward manufacturing process has enabled amputees to print their own prosthetics.26,27 This mode of prosthetic production could be an affordable and accessible solution for a large number of patients. However, no FDA approval currently exists for these 3D-printed devices, and regulation on their distribution is lacking.27 A systematic review evaluating the clinical efficacy of 3D-printed upper limb prosthetics concluded that all studies meeting inclusion criteria failed to compare the 3D-printed prosthetics with currently available products or production methods, and only one article had sufficient power to detect clinically significant effects.26 These studies did report favorable outcomes from the patient perspective and encourage the use of 3D printing as a new avenue for customized prosthetic development. New Noncustom Implants Three-dimensional printing technology can be used to produce orthopaedic implants that are not customized. Several new implant types for hip and knee arthroplasty have entered the market as a result of the streamlined 3D printing production process. Three-dimensional printed acetabular cups are thinner and less expensive than traditionally manufactured cups.28 A recently published study on a small group of patients who underwent revision of an acetabular defect with a 3D-printed acetabular cup reported improved stability, better hip scores, and decreased pain.29 The increased porosity and homogenous aperture of the 3D-printed cup have been hypothesized to facilitate bone growth better than traditionally manufactured cups.29 In a similar fashion, 3D printing has led to the development of porous metal implants for foot and ankle arthrodesis. These implants serve as an alternative to traditional plates, screws, and staples, providing sufficient structural support and improved surface for biological incorporation.30 Additive manufacturing has provided new strategies to refine the shape, rigidity, and material of new, innovative cage prototypes of interbody cages for spine surgery. The goal was to create a product that more accurately reflects properties of native bone. Preliminary studies evaluating mechanical properties of 3D-printed intervertebral fusion cages have found that they closely mimic the compressive modulus of trabecular bone.31 After implantation of a 3D-printed lamellar titanium cage packed with bone graft, a particular study found a 98.9% arthrodesis rate at 1 year in 93 patients undergoing spinal fusion.32 Patient-specific Instrumentation Customized surgical guides for orthopaedic surgery have been manufactured with the aid of 3D printing technology.33,34 Although it has been proposed that PSI reduces operative time and improves alignment, studies of total knee arthroplasty (TKA) demonstrated mixed results.35,36 To preserve a high standard of patient care with a growing case load, an in-depth investigation into the economic efficiency of PSI is valuable. A randomized controlled trial of TKA analyzed the efficiency of conventional instrumentation, PSI, and single-use instrumentation. Cases were classified into four groups: conventional/reusable, patientspecific/reusable, conventional/single-use, and patientspecific/single-use instrumentation. Patient-specific/reusable instrumentation was the most expensive but demonstrated good outcomes: shorter surgery times, less blood loss, shorter length of stay, and higher Oxford Knee Scores 6 weeks postoperatively.37 Single-use instrumentation prevented sterilization complications and avoided excess costs related to instrumentation but had no effect on efficiency.37 Whether PSI in primary TKA has a definitive advantage is still unclear; however, a recent review found that most publications on this topic do not claim a significant advantage of its use, yet they did not identify a completely negative impact on the accuracy of the procedure either.38 Three-dimensional printed patient-specific cutting jigs enable precise and accurate preoperative planning in complex cases of deformity. Correcting angular and rotational deformity can be challenging and requires intense preoperative planning. Clinical outcomes often depend on the accuracy of correction. Three-dimensional Figure 3 Finished three-dimensional printed implants. The extra titanium powder is brushed away and can be reused. 4 Journal of the AAOS Global Research & Reviews® ----- April 2021, Vol 5, No 4 ----- © American Academy of Orthopaedic Surgeons Three-dimensional Printing in Orthopaedic Surgery
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